Re: [PATCH 08/19] hw/misc/bcm2835_thermal: Add a dummy BCM2835 thermal sensor

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 10/8/19 1:36 PM, Alex Bennée wrote:
> Philippe Mathieu-Daudé <f4bug@amsat.org> writes:
> 
>> We will soon implement the SYS_timer. This timer is used by Linux
>> in the thermal subsystem, so once available, the subsystem will be
>> enabled and poll the temperature sensors. We need to provide the
>> minimum required to keep Linux booting.
>>
>> Add a dummy thermal sensor returning ~25°C based on:
>> https://github.com/raspberrypi/linux/blob/rpi-5.3.y/drivers/thermal/broadcom/bcm2835_thermal.c
>>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>> checkpatch warning:
>> WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
>> This is OK because the regex are:
>>
>>    F: hw/*/bcm283*
>>    F: include/hw/*/bcm283*
>> ---
>>   hw/misc/Makefile.objs             |   1 +
>>   hw/misc/bcm2835_thermal.c         | 109 ++++++++++++++++++++++++++++++
>>   include/hw/misc/bcm2835_thermal.h |  27 ++++++++
>>   3 files changed, 137 insertions(+)
>>   create mode 100644 hw/misc/bcm2835_thermal.c
>>   create mode 100644 include/hw/misc/bcm2835_thermal.h
>>
>> diff --git a/hw/misc/Makefile.objs b/hw/misc/Makefile.objs
>> index a150680966..c89f3816a5 100644
>> --- a/hw/misc/Makefile.objs
>> +++ b/hw/misc/Makefile.objs
>> @@ -53,6 +53,7 @@ common-obj-$(CONFIG_OMAP) += omap_tap.o
>>   common-obj-$(CONFIG_RASPI) += bcm2835_mbox.o
>>   common-obj-$(CONFIG_RASPI) += bcm2835_property.o
>>   common-obj-$(CONFIG_RASPI) += bcm2835_rng.o
>> +common-obj-$(CONFIG_RASPI) += bcm2835_thermal.o
>>   common-obj-$(CONFIG_SLAVIO) += slavio_misc.o
>>   common-obj-$(CONFIG_ZYNQ) += zynq_slcr.o
>>   common-obj-$(CONFIG_ZYNQ) += zynq-xadc.o
>> diff --git a/hw/misc/bcm2835_thermal.c b/hw/misc/bcm2835_thermal.c
>> new file mode 100644
>> index 0000000000..bac23f21ea
>> --- /dev/null
>> +++ b/hw/misc/bcm2835_thermal.c
>> @@ -0,0 +1,109 @@
>> +/*
>> + * BCM2835 dummy thermal sensor
>> + *
>> + * Copyright (C) 2019 Philippe Mathieu-Daudé <f4bug@amsat.org>
>> + *
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + */
>> +#include "qemu/osdep.h"
>> +#include "hw/sysbus.h"
>> +#include "hw/misc/bcm2835_thermal.h"
>> +#include "qemu/log.h"
>> +#include "qapi/error.h"
>> +#include "hw/registerfields.h"
>> +
>> +REG32(CTL, 0)
>> +FIELD(CTL, POWER_DOWN, 0, 1)
>> +FIELD(CTL, RESET, 1, 1)
>> +FIELD(CTL, BANDGAP_CTRL, 2, 3)
>> +FIELD(CTL, INTERRUPT_ENABLE, 5, 1)
>> +FIELD(CTL, DIRECT, 6, 1)
>> +FIELD(CTL, INTERRUPT_CLEAR, 7, 1)
>> +FIELD(CTL, HOLD, 8, 10)
>> +FIELD(CTL, RESET_DELAY, 18, 8)
>> +FIELD(CTL, REGULATOR_ENABLE, 26, 1)
>> +
>> +REG32(STAT, 4)
>> +FIELD(STAT, DATA, 0, 10)
>> +FIELD(STAT, VALID, 10, 1)
>> +FIELD(STAT, INTERRUPT, 11, 1)
>> +
>> +#define THERMAL_OFFSET_C 412
>> +#define THERMAL_COEFF  (-0.538f)
>> +
>> +static uint16_t bcm2835_thermal_temp2adc(int temp_C)
>> +{
>> +    return (temp_C - THERMAL_OFFSET_C) / THERMAL_COEFF;
>> +}
>> +
>> +static uint64_t bcm2835_thermal_read(void *opaque, hwaddr addr, unsigned size)
>> +{
>> +    Bcm2835ThermalState *s = BCM2835_THERMAL(opaque);
>> +    uint32_t val = 0;
>> +
>> +    switch (addr) {
>> +    case A_CTL:
>> +        val = s->ctl;
>> +        break;
>> +    case A_STAT:
>> +        val = FIELD_DP32(bcm2835_thermal_temp2adc(25), STAT, VALID, true);
>> +        break;
>> +    default:
>> +        g_assert_not_reached();
> 
> Will a unaligned read already have faulted and delivered an exception to
> the guest? As this access it controlled by the guest it could
> potentially take down QEMU. Perhaps it should be a LOG_GUEST_ERROR as
> bellow?

MemoryRegionOps::(valid|impl).unaligned default to false, so unaligned 
accesses won't reach this device, the guest will get a MEMTX_DECODE_ERROR.

>> +    }
>> +    return val;
>> +}
>> +
>> +static void bcm2835_thermal_write(void *opaque, hwaddr addr,
>> +                                  uint64_t value, unsigned size)
>> +{
>> +    Bcm2835ThermalState *s = BCM2835_THERMAL(opaque);
>> +
>> +    switch (addr) {
>> +    case A_CTL:
>> +        s->ctl = value;
>> +        break;
>> +    default:
>> +        qemu_log_mask(LOG_GUEST_ERROR, "%s: write 0x%" PRIx64
>> +                                       " to 0x%" HWADDR_PRIx "\n",
>> +                       __func__, value, addr);
>> +    }
>> +}
>> +
>> +static const MemoryRegionOps bcm2835_thermal_ops = {
>> +    .read = bcm2835_thermal_read,
>> +    .write = bcm2835_thermal_write,
>> +    .impl.max_access_size = 4,
>> +    .valid.min_access_size = 4,
>> +    .endianness = DEVICE_NATIVE_ENDIAN,
>> +};
>> +
>> +static void bcm2835_thermal_realize(DeviceState *dev, Error **errp)
>> +{
>> +    Bcm2835ThermalState *s = BCM2835_THERMAL(dev);
>> +
>> +    memory_region_init_io(&s->iomem, OBJECT(s), &bcm2835_thermal_ops,
>> +                          s, TYPE_BCM2835_THERMAL, 8);
>> +    sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);
>> +}
>> +
>> +static void bcm2835_thermal_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +
>> +    dc->realize = bcm2835_thermal_realize;
>> +}
>> +
>> +static const TypeInfo bcm2835_thermal_info = {
>> +    .name = TYPE_BCM2835_THERMAL,
>> +    .parent = TYPE_SYS_BUS_DEVICE,
>> +    .instance_size = sizeof(Bcm2835ThermalState),
>> +    .class_init = bcm2835_thermal_class_init,
>> +};
>> +
>> +static void bcm2835_thermal_register_types(void)
>> +{
>> +    type_register_static(&bcm2835_thermal_info);
>> +}
>> +
>> +type_init(bcm2835_thermal_register_types)
>> diff --git a/include/hw/misc/bcm2835_thermal.h b/include/hw/misc/bcm2835_thermal.h
>> new file mode 100644
>> index 0000000000..f85cce7214
>> --- /dev/null
>> +++ b/include/hw/misc/bcm2835_thermal.h
>> @@ -0,0 +1,27 @@
>> +/*
>> + * BCM2835 dummy thermal sensor
>> + *
>> + * Copyright (C) 2019 Philippe Mathieu-Daudé <f4bug@amsat.org>
>> + *
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + */
>> +#ifndef HW_MISC_BCM2835_THERMAL_H
>> +#define HW_MISC_BCM2835_THERMAL_H
>> +
>> +#include "hw/qdev-properties.h"
>> +#include "hw/sysbus.h"
>> +
>> +#define TYPE_BCM2835_THERMAL "bcm2835-thermal"
>> +
>> +#define BCM2835_THERMAL(obj) \
>> +    OBJECT_CHECK(Bcm2835ThermalState, (obj), TYPE_BCM2835_THERMAL)
>> +
>> +typedef struct {
>> +    /*< private >*/
>> +    SysBusDevice parent_obj;
>> +    /*< public >*/
>> +    MemoryRegion iomem;
>> +    uint32_t ctl;
>> +} Bcm2835ThermalState;
>> +
>> +#endif
> 
> Otherwise:
> 
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Thanks :)